The present invention relates to an apparatus for mounting and demounting a large nut and, more particularly, to an apparatus for removing and/or remounting (referred to as "handling", hereinafter) a large fastener, such as, for example, a nut onto a stud bolt, both of which are used for a pressure vessel such as a nuclear reactor.
In, for example, Japanese Patent Application No. 204606/1982, a nut handling operation is automatically carried out by a machine, with the purpose of the nut handling operation being for reducing an exposure of the operator to contaminants; however, a disadvantage of this proposed construction resides in the fact that, another machine is required for transporting nuts and washers to the desired positions.
Accordingly, it is an object of the present invention to provide an apparatus for handling fasteners such as, for example, nuts employed on a nuclear reactor pressure vessel under remote control without any need for access by an operator to the high radiation level area, and which is capable of transporting the removed nut to a desired position and a nut to be mounted to a predetermined position on the pressure vessel.
Another object of the present invention resides in providing an apparatus capable of automatically handling a nut together with an associated washer while simultaneously accomplishing the first-described object.
Yet another object of the present invention resides in providing an apparatus which is capable of reducing the magnitude of impact applied in a nut handling operation, while simultaneously accomplishing the first-described object.
In accordance with the present invention, an apparatus for removing and remounting large fastener means such as nuts comprises a circumferentially and radially movable station, a vertically movable frame close to and spaced from the station through a lifting means, a motor mounted on the frame, and a nut driving means provided with pawls, each of which is engageable with a radial groove formed on an end surface of the large nut, and provided at a distal end portion thereof with a nut retaining means. A transmission means transmits a driving force from the motor to the nut driving means to remove and remount the large nuts through the pawls.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings.